In hardware for broadcast receiving apparatuses represented by a television and a Set Top Box (STB), a configuration is adopted for realizing a greater function by forming an “information transfer path” series, where a plurality of devices having different functions are interconnected so that the output of one becomes the input of the other. For instance, taking the case of the outputting of images/sound onto a screen by a digital broadcast receiving apparatus, as an example, in terms of hardware, a “tuner device”, a “TS decoder device”, and an “AV decoder device” are connected, in the order of mention, to form an “information transfer path” series. The tuner device receives broadcast signals, and outputs a Motion Picture Expert Group-2 (MPEG-2) transport stream by filtering, using tuning information, such as frequency, or the like, as keys. The TS decoder device receives the MPEG-2 transport stream, and sorts out the MPEG-2 transport stream packet (hereinafter as TS packet) transmitting the desired video/audio data, from within the inputted MPEG-2 transport stream. It outputs a Packetized Elementary Stream (PES) packet containing the video/audio data transmitted by the matching TS packet. The AV decoder device receives the PES packet. It decodes the video/audio data transmitted by the PES packet, and outputs such decoded data in a form which can be displayed on-screen. Here, the accomplishment of the respective functions of each of the devices makes possible the display of images/sound onto a screen.
In order to carry out parallel processing in a broadcast receiving apparatus such as this, there are cases where a plurality of devices of the same type exists. For example, two tuner devices and two AV decoder devices exist, and these are connected to a TS decoder device. In addition, the TS decoder has a function for establishing “information transfer paths” in flexible combinations, with regard to the plurality of tuner devices and AV decoder devices. In such a case, it is possible to place the TS decoder device in between a tuner device A and an AV decoder device A to establish an “information transfer path 1”, and place the TS decoder device in between a tuner device B and an AV decoder device B to establish an “information transfer path 2”. In such a case, the “information transfer path 1” and the “information transfer path 2” demodulate MPEG-2 transport streams from a broadcast signal fully independently from one another, making possible the simultaneous decoding of a plurality of video/audio data, and enabling the realization of the so-called “Picture In Picture (hereinafter as PIP)” function for simultaneously displaying two types of images/sound on a single screen. In such devices, there is no necessity for implementing PIP at all times, and normally, single image display and PIP display can be switched, through inputs in a remote control, or the like, by a user. The “official publication of Japanese Laid-Open Patent Application No. 8-289220” is provided as a case in point for the method of use of each device, in cases such as the one above. This invention conceives a method for realizing PIP in a broadcast receiving apparatus having two tuner devices, one AV decoder, and one PIP data processing device. In this invention, the two tuners are ranked as a “main tuner” and an “insert screen tuner”, and using the “insert screen tuner” during PIP display, enables the outputting of video/audio considered for selection, on a specified area of the screen, while the video/audio already selected, remains displayed on the entirety of the screen.
At present, a standard, referred to as Digital Video Broadcasting-Multimedia Home Platform (DVB-MHP), for operating an application on a broadcast receiving apparatus has been defined in Europe, and its operation has already begun. On the other hand, in the United States, Open Cable Application Platform (OCAP) standard, based on the DVB-MHP standard, is being laid out, and is scheduled to start operation sometime in 2005. In addition, the development and operation of similar standards is being pursued in other countries. A broadcast receiving apparatus, conforming to such application execution standards, is equipped with a function for executing a program obtained using a method such as downloading from a broadcast signal, and so on. Typical examples that can be given for such programs are games, Electrical Program Guide (EPG) applications, and so on.
Naturally, applications which simultaneously display a plurality of video/audio data on a single screen, such as the aforementioned PIP, advanced function EPG, and so on, are assumed as programs for execution on broadcast receiving apparatuses capable of program execution. In order to output a plurality of video/audio data simultaneously on a single screen, as represented in the example disclosed in the aforementioned patent, the control of multiple devices, particularly the setting of the “information transfer path” of each device, must be performed properly. In OCAP/DVB-MHP API (Application Program Interface), the function for individually controlling a tuner device, a TS decoder device, an AV decoder device, and so on, is already provided, and the implementation of such an application is not impossible, even under current conditions. Unfortunately, there is no function for setting an “information transfer path” between the individual devices in the current standard. For example, it is not possible to perform a designation to establish an “information transfer path” between a tuner device A, from among a plurality of tuner devices, and a certain TS decoder device B, from among a plurality of TS decoder devices. In OCAP/DVB-MHP, during video/audio outputting, for example, first the demodulation of an MPEG-2 transport stream transmitting video/audio data for outputting is set by furnishing tuning information such as frequency, and so on, to the tuner device. Next, an identifier for the video/audio data to be outputted to the AV decoder is set. At this point, a program, referred to as “middleware” (hereinafter as OCAP/DVB-MHP middleware), for implementing the functions prescribed in the OCAP/DVB-MHP standard by using the functions found in the OS of a broadcast receiving apparatus, searches within the broadcast receiving apparatus for the tuner device that outputs the MPEG-2 transport stream that includes the video/audio data pointed out by the identifier designated by the AV decoder. If such tuner device is found, a TS decoder is placed in between, with respect to the two devices, and an “information transfer path” is implicitly established.
Standards such as these, relieve a program from complicated processes concerning device management, and at first glance, seem beneficial to a program. However, from an opposite viewpoint, the implicit establishment of “information transfer paths” by middleware means that the program is unable to manage “information transfer paths”. For example, consider the hardware configuration shown in FIG. 1. FIG. 1 illustrates a digital broadcast receiving apparatus having a structure with two tuners (tuner 101a and tuner 101b), and two AV decoders (AV decoder 103a and AV decoder 103b), which are respectively connected via a TS decoder 102. Consider the operation of a PIP program on the present hardware. In FIG. 1, since two tuners and two AV decoders exist in terms of hardware, if all of such devices are taken and two “information transfer paths”, between the tuner 101a and the AV decoder 103a, and between the tuner 101b and the AV decoder 103b, via the TS decoder 102, are established, a PIP program able to fully separate and switch two sets of images can be realized. However, in current OCAP/DVB-MHP middleware, there is no function for establishing “information transfer paths” between devices. At the point when a PIP program specifies video and audio data and issues a decode request, an “information transfer path” is implicitly established between an AV decoder and a tuner demodulating the MPEG-2 transport stream which includes such video and audio data, via a TS decoder. As such, for example, in the case where a decode request for video/audio data within the same MPEG-2 transport stream is issued to two AV decoders, it is possible to have “information transfer paths” being established between a single tuner and the two AV decoders. In terms of the example in FIG. 1, “information transfer paths” would be set, via the TS decoder 102, between the tuner 101a and the AV decoder 103a, as well as between the tuner 101a and the AV decoder 103b. In such a case, and additionally, in the case where the implementation of the OCAP/DVB-MHP middleware is such that an “information transfer path” established once between an AV decoder and a tuner is maintained, and where the “information transfer path” established first, is used for decode requests issued thereafter to AV decoders, the PIP program will only be able to use one tuner from then on, and the two AV decoders will only be able to simultaneously decode video data within the same MPEG-2 transport stream.
A method that promotes in middleware, the implicit establishment of “information transfer paths” between devices in the above manner, reduces the burdens related to device controlling for a program, but at the same time also reduces the flexibility with regard to device management. In addition, as shown in the example using FIG. 1, since the dependency of program operations on the implementation of middleware is increased, there is a possibility of causing such instability as having a program operate differently for each environment.